Serena Williams enter the U.S. Open as two-time defending champion, and likely has a chip on her shoulder.

With 17 grand slam titles in her career, Williams hasn't won a big one since last year's Open. Her failures in Australia, on the clay in Paris and the grass at Wimbledon gnaw on her. At 32, her era of dominance is drawing to a close.

Maria Sharapova (AP Photo)

Don't write Williams out among a strong field of women's title contenders. She remains the No. 1 player in world rankings and has every reason to rise with her best effort at the USTA Billy Jean King National Tennis Center. New York is her stage.

But when play begins Monday in the U.S. Open, younger women will be hot after Williams.

Topspin: At majors in 2014, lost in fourth round at Australian Open, second round at French Open, third round at Wimbledon. ... Two-time defending champion at U.S. Open; trying to win three consecutive titles at one of tennis' major tournaments for first time. ... Last woman with a "three-peat" in New York was Chris Evert, who won four trophies in a row from 1975-78.

Simona Halep

Seeded: 2

Ranked: 2

Age: 23

Country: Romania

2014 match record: 38-11

2014 singles titles: 2

Career singles titles: 8

Major titles: 0 — Best: F, French Open ('14)

Past 5 U.S. Opens: '13-4th, '12-2nd, '11-2nd, '10-1st

Topspin: Made only one third-round run in her first 13 career Grand Slam appearances, but starting with last year's U.S. Open, hasn't lost before the fourth round in her last four majors. ... Not much power to her game; relies instead on angles and court coverage.

Petra Kvitova

Seeded: 3

Ranked: 4

Age: 24

Country: Czech Republic

2014 match record: 28-12 (excluding Connecticut Open)

2014 singles titles: 1

Career singles titles: 12

Major titles: 2 — Wimbledon ('11, '14)

Past 5 U.S. Opens: '13-3rd, '12-4th, '11-1st, '10-3rd, '09-4th

Topspin: Trying to become the first woman other than the Williams sisters to win Wimbledon and the U.S. Open in the same year since Martina Hingis in 1997. ... Tough draw includes first-round match against up-and-comer Kristina Mladenovic, possible third-rounder against big-hitting American Madison Key, and possible fourth-rounder against past major champions Victoria Azarenka or Svetlana Kuznetsova.

Maria Sharapova

Seeded: 5

Ranked: 6

Age: 27

Country: Russia

2014 match record: 38-9

2014 singles titles: 3

Career singles titles: 32

Major titles: 5 — U.S. Open ('06), Wimbledon ('04), French Open ('12, '14), Australian Open ('08)

Last 5 U.S. Opens: '13-DNP, '12-SF, '11-3rd, '10-4th, '09-3rd

Topspin: Missed last year's tournament with an injury to her right shoulder, which has given her trouble off and on over the past several seasons. ... Winning 46.2 percent of her return games this season, fifth-best on tour.

Eugenie Bouchard

Seeded: 7

Ranked: 8

Age: 20

Country: Canada

2014 match record: 37-17

2014 singles titles: 1

Career singles titles: 1

Major titles: 0 — Best: F, Wimbledon ('14)

Past 5 U.S. Opens: '13-2nd, '12-DNP, '11-DNP, '10-DNP, '09-DNP

Topspin: Only woman to reach at least the semifinals at all three Grand Slam tournaments in 2014, including first major final at Wimbledon last month. ... Only 1-3 on hard courts in run-up to U.S. Open. ... Does not rank in top 10 of WTA this season in any of 10 significant serve or return statistical categories.

Topspin: Making her 64th career Grand Slam appearance, most among active players and tied for third in the Open era, behind Amy Frazier's 71. ... Run to final in Montreal in August — which included victory over younger sister Serena — showed that she can still summon hard-court success.

Sloane Stephens

Seeded: 21

Ranked: 22

Age: 21

Country: United States

2014 match record: 20-18

2014 singles titles: 0

Career singles titles: 0

Major titles: 0 — Best: SF, at Australian Open ('13)

Past 5 U.S. Opens: '13-4th, '12-3rd, '11-3rd, '10-DNP, '09-DNP

Topspin: Considered "next big thing" in U.S. tennis, has taken a step back this season, including first-round loss at Wimbledon that ended streak of six second-week appearances at majors. ... Tends to enjoy big stages, and game works well on hard courts, so could make a move at Flushing Meadows, if able to get past potential third-rounder against 2008 runner-up Jelena Jankovic.